This project will continue the development of general procedures for toxic residue detection which are designed to detect any unknown member of broad chemical classes of toxic sbstances when the presence of that compound is not suspected. The methodology involves the application of negative chemical ionization (NCI) mass spectrometry after subjecting environmental substrates to minimal and specific cleanup procedures for each class of toxic substances. The fact that NCI mass spectra are virtually transparent for biomolecule and very sensitive to the presence of toxic substances will be used to detect the molecules in question. NCI mass spectra of partially cleaned up environmental substrates will be matched by computer to a library of NCI spectra of toxic substances which will be developed during this project. The toxic substances in the spectra library will include those samples available from the EPA repository of toxic substances and those available from the National Cancer Institute repository of carcinogens. Specific cleanup procedures will be developed which do not involve adsorption chromatography for polychlorinated organics, nitrosamines and nitrosamides, phosphates and phosphothioates, carbamates, and polycyclic fungal toxins. Procedures for aqueous and lipid rich substrates will be developed. The sensitivity for all compounds in the NCI mass spectral library will be determined under standard operating conditions. The amount of recovery of selected examples of toxic substances in the classes examined will be determined. We will develop a new specific detector for N-nitroso compounds and test its sensitivity and freedom from artifacts. The detector will be based on photoionization detection of nitric oxide generated by thermolysis or photolysis of the N-nitroso compounds. We will develop a confirmation protocol for samples tentatively identified in the NCI screening procedure. This protocol will involve gas chromatography mass spectrometry and simple gas chromatography for confirmation and quantitation of identified unknowns.